1. Field of the Invention
This invention concerns electronic commutation for a brushless D.C. motor having a Y-connected stator.
2. Description of the Prior Art
Such a brushless D.C. motor is shown in the German publication, ETZ, 1972, pages 295 and 298. A separate control stage, cyclically controlled by a current regulator, is provided for the current control of this motor. Cyclic control has the advantage over continuous control in that the losses are lower and higher efficiency is thereby achieved. This advantage is counterbalanced, however, by the cost of separate control stage.
Deutsche Auslegeschrift No. 1,244,933 shows a brushless D.C. motor in a bridge circuit, in which the cyclic control of the current is effected directly by means of an electronic commutation device and therefore, no separate control state is required. By-pass diodes are connected parallel to the two commutation devices so that the current can continue to flow in the motor winding during the current intervals. Such a circuit design is not possible, however, for brushless D.C. motors with a Y-connected stator winding.
It is an object of this invention to provide a brushless D.C. motor with a Y-connected stator winding and cyclic current control, in which the current can be controlled directly by means of an electronic commutation device.